IL-1β induces a pro-inflammatory fibroblast micro-environment that impairs alveolar epithelial organoid formation
Cellular and molecular mechanisms (English)Chronic Obstructive Pulmonary Disease (COPD) is characterized by a chronic inflammatory state in the lungs that leads to small airway remodelling and emphysema due to defective tissue repair. We aimed to investigate how this inflammatory microenvironment affects the molecular signalling between mesenchymal niche cells and epithelial progenitor cells in the distal lung, leading to impaired regenerative potential. We focused on IL-1β, a key inflammatory mediator, and hypothesize that IL-1β could “reprogram” the fibroblast niche in the alveolar compartment.
Lung fibroblasts (MRC-5) were treated with IL-1β for 24 hours, subsequently gene expression was assessed by qRT-PCR and production of pro-inflammatory cytokines was assessed by ELISA.
Next, we applied a lung organoid assay, and MRC-5 pre-treated with IL-1β for 24 hours were thoroughly washed and co-cultured with primary mouse distal lung epithelial cells (Epcam+) in Matrigel in a Transwell insert. After 14 days, organoids were stained for pro-surfactant protein C (SPC) and Acetylated tubulin (ACT) markers to investigate alveolar or airway phenotype respectively, and organoids number and size were quantified.
We observed a significant and dose-dependent upregulation of growth factors involved in mesenchymal-epithelial signalling, such as FGF7 and FGF2, and downregulation of FGF10 transcripts in fibroblasts treated with IL-1β. In addition, a substantial (>100 fold) upregulation of the pro-inflammatory cytokines IL-8 and IL-6 was also observed and confirmed by ELISA, further confirming IL-1β as an important trigger for an inflammatory response in fibroblasts.
Organoids derived from IL-1β pre-treated fibroblasts were significantly lower in number and smaller in size (not significant). Furthermore, number of SPC+ organoids was significantly lower than control, while ACT+ was higher but not significant.
These data show that IL-1β is capable of altering the fibroblasts’ state, and suggest that these changes reduce their supportive function in co-culture with alveolar progenitor cells, which may thus contribute to impaired alveolar repair.